The present invention relates to a hydrodynamic coupling having a pump wheel and a turbine wheel which together form a toroidal working space for a hydraulic working fluid and further having a storage chamber for the hydraulic working fluid.
Couplings of this type have become known from a number of publications. The working space and storage chamber are in fluid communication with each other. Upon start-up of the drive motor driving the coupling, the storage chamber applies working fluid to the working space after a certain delay whereby the initial transmission of driving torque occurs very gently so that the components involved and particularly the drive motor are not overly stressed. Reference is made to the following documents:
(1) GB-A 922 415 PA1 (2) GB-A 1 000 565 PA1 (3) EP 062 274 A3
Hydrodynamic couplings using a constant quantity of working fluid (construction T) are generally used as starting and overload couplings.
In these known hydrodynamic or turbocouplings there is a dependence between the torque transmitted and the slippage which occurs between the pump wheel and turbine wheel. The torque which can be transmitted with a predetermined slippage is determined by the amount of working or coupling fluid introduced into the working space and the drive speed.
In these known couplings, a change in the coupling fluid admission into the working space during operation in order to change the torque/surface ratio at a constant drive speed is not possible. Furthermore, it is not possible to disconnect the output drive during operation.
In the known couplings, the starting torque can, for instance, be reduced by a delay chamber. The working space and delay chamber are in fluid communication with each other via nozzles. Depending on the dimensioning of the nozzles, working fluid passes faster or slower out of the delay chamber into the working space. In this way, the increase of the torque over time can be influenced.
This type of coupling offers the advantage of removing heat via the surface of the coupling since the fluid circuit enclosing parts rotate in air and can be optimized for cooling by suitable shaping.
In contrast to couplings with a constant quantity of working fluid, there are also couplings in which the working fluid is taken from an external container. In these couplings, the rotating coupling parts are surrounded by a stationary, oil-tight housing. In this way, the rate of admission of fluid into the coupling with constant drive speed can be varied and thus the torque-slippage ratio can be varied.
These applications are generally used for adjusting the speed of rotation of the output shaft. The heat produced is removed via an external cooling device.